'99 Sierra Idle Problem

I am getting a low idle issue on my '99 Sierra 5.3L w/109k miles. It
normally idles ~700RPM, but is not sporadically idling at 300 RPM which is
causing it to stall. What things should I be looking at as a possible

cause. Nothing has been changed in the motor except the plugs which I
changed 10k miles ago.
Thanks in Advance,
-a12vman

Put a realtime scanner on it and my guess is that you will find that
you have a idle timing issue. My 2000 K3500 would do that sometimes at
certain engine temps and it thru no codes and dealer said it was fine.
It turned out that the ECM was retarding the spark at times to as much
as 20 ATC at a idle and it would slow engine way down, WIth a
reraltime data scanner you can whatch the engine timing and see if it
is the culprit too.
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